Medical imaging methods such as ultrasound, MRI, CT or PET often provide the possibility of acquiring three-dimensional image data sets of certain areas of the body. In the case of moving organs, such as the heart, the major arterial blood vessels or any other organs subjected to cardiac or respiratory movement, many medical imaging methods allow the acquisition of dynamic four-dimensional image data sets, which contain three-dimensional image information of the object at different time points (e.g. moving heart).
However, when viewing and assessing the acquired volume data, most medical practitioners resort to two-dimensional images again, because they are used to forming a diagnosis on the basis of certain two-dimensional views. For example, in case of the heart, examination is carried out using specifically aligned cuts through the heart chambers, for example the four-chamber view, the two-chamber view, long axis views and short axis views. The long axis extends from the apex to the base of the heart, while short axis views are perpendicular to the long axis views.
A state of the art method for assessing anomalies in the left ventricle is to reconstruct a series of short axis views through the left ventricle from four-dimensional dynamic image data sets acquired by ultrasound. In other applications, for example MRI, the short axis views may be directly acquired from the heart. In both cases, assessment of the viability of the ventricle wall is considerably complicated by the movement of the heart. Since the short-axis sectional planes stay fixed in space while the heart moves through them, the part of the ventricle wall which is visible in a certain short axis view is not constant over time. Thus, an apparent bulge or swelling in the ventricle wall may be caused simply by the movement of a different part of the heart into the field of view.
Further, the long axis is a straight line, with the short axis views being perpendicular thereto. However, a straight line does not conform well to the shape of the heart chambers, in particular the left ventricle, since these are often not straight ellipses, but “banana”-shaped towards the apex. Thus, the conventionally generated short axis views often have an unfavorable angle to the myocardial wall. This situation is exacerbated by the fact that the ventricles often perform complicated translational and rotational movements during contraction. Thus, movements of the heart chamber may wrongly be interpreted as pathological alterations in the heart.